That's a big change, so it should be a 2.0 version of the kit. Will be released as a beta first.
Build
BEFORE: JS files with code in closures, writing to an "export" object different depending on the environment, simply concatenated
AFTER: CommonJS modules directly usable by NodeJS, Browserify and Webpack, plus a file built by Browserify to use it simply with a script tag
BENEFITS: less boilerplate, explicit dependencies between the files, easier to maintain
New features
ES6 Promises: functions taking a callback now also return a promise. Backward compatibility to maintained because the callback can still be used. NodeJS already supports them, the compiled file includes a polyfill, but if you're including the kit in your Browserify or Webpack build you should get a polyfill if you want to support IE11 or below (whether or not you use promises).
Compatibility
Should be backward-compatible
Some internal classes that were exposed are no longer visible
ESlint
Only matters if you're hacking the kit itself: we're now using eslint to check correctness and style
That's a big change, so it should be a 2.0 version of the kit. Will be released as a beta first.
Build
New features
Compatibility
ESlint